is "proper social etiquette" applicable to immediate family?

I'll be honest, I sometimes miss social cues and don't always know what's "proper" but I try.

Here's the story-

My sister has made some really pretty cakes over the years for my nieces birthdays. So I figured I'd ask her if she minded making one for my first babies first birthday. She said she would think about it and get back to me. So today, she calls me.

"Robyn honey, you know I love you, and I'm going to make the cake, but it's really not proper social etiquette to ask people to make things for a your party."

To which I said "I only asked bc you've made some really pretty cakes in the past. If it really bothers you, I'll pay you for it."

She said nooo is fine, I'm just saying, that's not what people do.


I asked a friend what she thought, she said it's totally normal to ask, even a friend if someone is good at something.


So what do you think? Was I rude for asking, and acting entitled, or is my sister wrong?